A known developing device used in an image forming apparatus includes a housing for accommodating developer therein, a developing roller rotatably held in the housing, a layer thickness regulation blade contacting the developing roller and a seal member arranged between the housing and the developing roller (see, for example, JP-A-2010-164736). In this developing device, the layer thickness regulation blade has a blade main body made of sheet metal and a blade rubber part protruding from the blade main body and contacting the developing roller.
The seal member is provided in a shape following an outer peripheral surface of the developing roller and one end thereof is adhered to each end portion of the blade main body. Further, an end surface of the seal member at an inner side in an axial direction of the developing roller is in contact with an end surface of the blade rubber part at an outer side in the axial direction of the developing roller.